The generation of neuronal diversity in the nervous system requires the specification and differentiation of a multitude of cellular lineages. Successive developmental programs control the generation of individual neuronal types, cell migration, axon extension, and ultimately the formation of functional synaptic connections. The specific genetic programs underlying the differentiation of mature neurons from their progenitors remain incompletely characterized, in part because of the difficulty in studying neuronal progenitor cells in their native environments. In the vertebrate olfactory system, primary sensory neurons are continuously regenerated throughout adult life via the proliferation and differentiation of multipotent neural progenitor cells. This feature makes the olfactory system particularly amenable for studies on the properties of neuronal stem cells. While distinct stages of the olfactory lineage have been identified with a limited set of molecular markers, much remains to be learned about the genetic programs that both define and regulate olfactory neurogenesis during development and regeneration. To date, nothing is known about the transcriptional networks regulating the multipotent olfactory progenitors, the earliest cells in the lineage. Elucidation of these regulatory networks is critical for understanding how mature neuronal and non-neuronal cell types are generated from the adult tissue stem cell of the olfactory epithelium. In this application we propose to investigate the role of the transcription factor p63 - a member of the p53 family of tumor suppressors - in olfactory stem cell regulation. Through whole genome transcriptome profiling and genetic loss-of-function analysis, we recently discovered that p63 is a key regulator of olfactory stem cell self-renewal and differentiation in vivo, similar to its established role in other epithelial stem cells. Here we propose to investigate the cellular and molecular actions of p63 in the olfactory stem cell. Specifically, we will (1) determine the role of p63 in the choice between self-renewal and differentiation;(2) determine whether p63 and its related family member p53 interact to regulate olfactory stem cell dynamics;and (3) characterize the p63-dependent transcriptional network regulating the olfactory stem cell by identifying the downstream targets of p63. Together these investigations will illuminate the cellular and molecular mechanisms regulating olfactory stem cell maintenance, proliferation and differentiation. Moreover, our studies will provide a model for understanding the mechanisms regulating other neural stem cell types and lay the groundwork for the future development of treatments and therapeutics to ameliorate neural tissue damage and degeneration. PUBLIC HEALTH RELEVANCE: The proposed research will define and characterize the genetic interactions regulating neurogenesis and tissue regeneration in the olfactory epithelium. This information is critical for an understanding of the causes of degenerative diseases and injuries resulting from the misregulation of these processes, and will lay the foundation for future strategies aimed at ameliorating neurodegenerative disorders and traumatic injuries by identifying new therapeutic targets and potential cell replacement therapies.